At the University of Illinois, we have a colony of 28 insulin-dependent diabetic rhesus monkeys induced by streptozotocin or pancreatectomy. These animals have been diabetic for 1 to 13 years. We propose to examine the retina of these animals in 3 directions: I. To define the clinical, physiologic and pathologic changes in the retina, retinal pigment epithelium and choroid of these chronically diabetic animals; II. Two systemic factors affecting diabetic retinopathy will be examined: 1) systemic hypertension, and 2) hyperlipidemia; III. Two ophthalmic manipulations, namely 1) cataract extraction, and 2) laser photocoagulation, will be applied to the retina of these animals. The retina of these animals will be studied by clinical, physiologic and pathologic methods. Currently, we have one naturally diabetic rhesus monkey. We shall do a detailed clinical, physiologic and pathologic study on the retina of this animal. It is estimated that we may obtain one naturally diabetic primate a year through our various veterinary connections (see attached letter from Dr. Bennett). This naturally diabetic model will further complement our study of an experimental model of chronically diabetic primates, induced by pancreatectomy or streptozotocin. The ultimate goal of the research project is to study the pathology and pathogenesis of diabetic retinopathy in an effort to define the earliest pathologic changes, and its progression under various ophthalmic or systemic contributing factors.